This invention is directed to a lock mechanism and more particularly to a lock mechanism used in the narrow stiles of high security doors generally used in non residential type buildings.
While a wide variety of high security lock mechanisms have been disclosed, style AR1850 marketed by Adams Rite Manufacturing Company of Glendale, Calif., is in very wide use almost to the exclusion of other locking mechanisms. This lock mechanism is described in U.S. Pat. No. 4,218,903 to Eads, assigned to Adams Rite. For the past 40 years lock mechanisms used on narrow stile doors including sliding doors have been reported to have some serious security problems as a result of their mechanical design. Various costly external devices have been devised to deal with several of these problems. These devices are only marginally effective. Common techniques used to unlawfully open these locks include using a wrench to twist the lock cylinder breaking the set screw holding the cylinder from turning. Rotating ring collars that are recommended to prevent using this technique add expense and are only marginally effective in deterring wrenching the cylinder. A second method is to drill a hole through the wall of the door stile into which a probe aligned with the spring latch is used to disengage the spring loaded latch of the lock. Using a third method these types of locks are also susceptible to the use of a hook constructed of flat spring steel, which in the hands of a skilled burglar, allows easy entry into the premises. A fourth method requires no mechanical skill. This method does require the person to gain access to the lock while it is unlocked and surreptitiously insert a thin metal shim such that when the lock is engaged by the end user, the shim interferes with the latching mechanism. While the lock mechanism appears to be locked, slight shaking of the lock bolt causes the lock bolt to disengage. After entry, these locks can be relocked with an L-shaped tool, leaving no trace of illegal entry and thus reducing the chance of quick appropriate law enforcement action. While the first and second methods could be considered forced entry which leave evidence of the method used, the third and fourth methods leave no marks or evidence of how entry was accomplished. This is of particular concern for the end user leading to possible false conclusions such as that the door was left unlocked or that entry was made by use of a duplicate key.
The lock mechanism described in U.S. Pat. No. 4,218,903 to Eads, utilizes a retainer pin that is moved through an arcuate slot which in turn is engaged in a swinging actuator lever which moves the swinging bolt. The bolt is secured in the retracted unlocked position and in the extended locked position by a spring-urged latch. In U.S. Pat. No. 3,899,906 to Bradstock, with a casement type cylinder, an insertable lock mechanism using a rocker lever to transmit movement of the lock cylinder cam to a swingable bolt utilizes a spring-urged latch similar to Eads to maintain the bolt in a locked position. A standard lock mounting mechanism for narrow stile door frames is described in U.S. Pat. No. 3,479,851 to Davidson, et al. A swinging bolt construction described in U.S. Pat. No. 3,659,885 to Nail is a narrow stile latch-lock mechanism utilizing a swinging, pivoted hook operable by a latch handle and utilizing a swinging actuating lever to move the latch hook. In U.S. Pat. No. 4,126,341 to Bradstock, a self-contained electric power driven bolt actuating unit in a high security door utilizes a actuator shaft connected at one end with a bolt actuating cam utilizing a swinging actuator lever engaging the swinging bolt.
None of these devices satisfy the needs and associated problems with the present locking mechanisms or do not attain the objects described herein below.